The aim of this research is to isolate and characterize antigens in circulating immune complexes (CIC) from patients with acquired immunodeficiency syndrome and Kaposi's sarcoma (AIDS-KS) and to exploit these antigens for development of new diagonostic and prognostic reagents. The source of the CIC are eluates from columns of Staphylococcus aureus Cowan I protein A bound to a silica matrix (Prosorba[unreadable]TM[unreadable]), which have been perfused with up to 2 liters of patient plasma as part of a therapeutic protocol. Eluates from 60 procedures have been collected and over 300 other eluates will be collected in the next 6 months. CIC and IgG can be eluted from Prosorba[unreadable]TM[unreadable] columns and the CIC can be purified by sucrose gradient ultracentrifugation. Antigen and antibody can then be separated by centrifugation of CIC in sucrose gradients under conditions favoring dissociation of complexes. A common antigen has been isolated from CIC in three AIDS-KS patients; the same antigen was not found in CIC obtained from patients with other malignancies and normals. Heterologous anti-serum will be raised against this CIC-derived antigen and immunologic screens of sera from numerous cancer patients and normals will be performed to assess the distribution of the antigen. Phase II of the research will involve more extensive specificity testing, development of monoclonal antibodies against the antigen, location of cell lines expressing the antigen for production purposes, and development of a test kit for clinical application. A test for a serologic marker for AIDS-KS would make a major contribution to the clinical evaluation and management of this disease. (5)